Electroluminescent devices using organic thin films have been developed. An electroluminescent device using an organic thin film, namely, an organic electroluminescent device, generally includes an anode, a cathode, and an organic layer on a substrate. The organic layer is disposed between the anode and the cathode and contains at least a light-emitting layer. The organic layer is provided with, in addition to the light-emitting layer, a hole injection layer (anode buffer layer), a hole transport layer, a hole blocking layer, an electron transport layer, and an electron injection layer. In general, an organic electroluminescent device is constituted by laminating these layers between an anode and a cathode.
In known organic electroluminescent devices, fluorescence has been used. As an attempt to increase the luminous efficiency of a device, phosphorescence has been investigated to be used instead of fluorescence. However, sufficient luminous efficiency has not been practically achieved even if phosphorescence is used.
In many of known organic electroluminescent devices using phosphorescent molecules, materials containing carbazolyl groups are used as materials (host material) for the light-emitting layers. For example, in Appl. Phys. Lett., vol. 75, p. 4, 1999, a biphenyl derivative shown bellow is disclosed as a host material.

In an organic electroluminescent device using the above-mentioned biphenyl derivative, there is a tendency that recombination of charge carriers occurs at the cathode side and is not well balanced. Therefore, high luminous efficiency is not achieved.
In Japanese Unexamined Patent Application Publication No. 6-1972, it is disclosed that a compound shown below is used as an organic electroluminescent device.

This compound is observed to emit light under a high voltage only and is thought that the luminance and luminous efficiency are insufficient.
In Japanese Unexamined Patent Application Publication No. 2000-186066 and Japanese Unexamined Patent Application Publication No. 2000-169448, it is disclosed that a pyridine compound shown below is used as a fluorescent element or a hole-transporting material and/or a light-emitting layer material of an electrophotographic photoreceptor.

In Japanese Unexamined Patent Application Publication No. 2003-22893, it is disclosed that a compound shown below is used as a material for an organic electroluminescent device.

In International Patent Publication No. WO03/078541, it is disclosed that a compound shown below is used as a material for an organic electroluminescent device.

The compounds disclosed in these patent documents each include a structure in which a nitrogen atom in a carbazole ring can conjugate with a nitrogen atom in a pyridine ring, triazine ring, pyrimidine ring, or pyrazine ring. Therefore, polarization phenomenon of charges in molecules is significant and the triplet excitation level is relatively low. In addition, the durability of these compounds is not sufficient as a material for an organic electroluminescent element. Therefore, the performance of the compounds is insufficient for being applied to a blue light-emitting device or a phosphorescence-emitting device. Further, when compounds do not have a structure in which all of 2,4,6-positions of pyridine ring, 2,4,6-positions of pyrimidine ring, or 2,3,5,6-positions of pyrazine ring are substituted with substituents, the compounds are low in electrochemical durability.
In International Patent Publication No. WO03/080760, it is disclosed that a compound shown below is used as a material for an organic electroluminescent device.

In these compounds, one aromatic ring (here, a benzene ring) has two carbazolyl groups (which are electron-donating groups) located in the meta-position (m-position) of the aromatic ring not to conjugate with each other. Therefore, positive or negative charges are readily localized by electrically oxidizing or reducing the molecules. Therefore, these compounds are lack of durability against electrical oxidization/reduction. In addition, a pyridine ring or a pyrimidine ring is introduced to these compounds in order to improve the durability against electrical reduction. However, when an aromatic ring (here, a benzene ring) has two carbazolyl groups as substituents, the aromatic ring is located in the p-position with respect to the nitrogen atom in a pyridine ring or a pyrimidine ring and can conjugate with the pyridine ring or the pyrimidine ring. Consequently, due to the electron-donating effect of the aromatic ring to the pyridine ring or the pyrimidine ring, the pyridine ring and the pyrimidine ring are low in durability against electrical reduction.
International Patent Publication No. WO03/080760 discloses a compound shown below.

However, though it is predicted that the above-mentioned compound is improved in durability against electrical oxidization, the number of the carbazolyl group is only one and the hole-transporting property is thereby low. Consequently, the hole-transporting property and the electron transporting property are not well balanced as a material for a light-emitting layer of an organic electroluminescent device, and the compound is required to be improved when it is used as a host material. In addition, the compound has defects in the viewpoint of heat resistance, which is significant in a practical use.